Polycarbonate resins are well known engineering plastics and have long been used in a large variety of applications. In recent years, these resins have been used successfully as substrates for information storage and recording applications, most notably video and audio discs. Other applications include ophthalmic lenses and the like.
Much effort has been devoted to impart water-clarity to polycarbonate substrate used in data storage applications, e.g., compact discs. It has been observed that some mold release agents that are excellent performers in all respects often impart undesirable yellowness to the molded polycarbonate article. The preparation of a molding composition suitable for the preparation of optical discs meeting the requirements of clarity and color has long been an objective of the art-skilled.
The relevant art is noted to include U.S. Pat. No. 4,670,479, which disclosed a polycarbonate composition containing organic phosphine and a partial ester of a monobasic fatty acid. The disclosed composition is said to be suitable in presently relevant applications.
U.S. Pat. Nos. 4,325,863 and 4,338,244 disclosed a benzofuranone compound useful as stabilizer for organic materials. The organic polymeric materials stabilized by this compound are said to include polycarbonates. Also relevant are U.S. Pat. Nos. 5,175,312 and 5,607,624, which disclosed 3-phenylbenzofuran-2-ones and 3-arylbenzofuranones respectively, said to be suitable as stabilizing agents for organic materials against oxidative, thermal or light induced degradation.
The present invention resides in the findings that a polycarbonate composition containing the specified ester and a stabilizing compound having at least one benzofuran-2-one group in its molecular structure is particularly suitable for the preparation of optical storage devices having attractive optical properties.